1. Field of the Invention
This invention relates to insulation devices for pipes; more particularly, to an insulation device for surrounding the uninsulated, adjoining end portions of preinsulated pipe.
2. Description of the Prior Art
Above-ground and undersea pipeline systems have assumed increased importance, particularly in the oil and gas industry where it is necessary to transport fluids from well-heads located in remote, extremely cold regions, such as Alaska, to seaports or processing facilities. Often sea water likewise is transported by pipeline to a well-head to replace extracted oil and gas, and thereby maintain pressure. In these circumstances, a buried pipeline is impractical because the pipeline must traverse the earth's permafrost layer which remains frozen. The fact that a pipeline is above-ground often means that the fluid being transported is at a temperature substantially higher than ambient temperature; therefore, the pipeline must be insulated to prevent undue heat loss from the fluid during transport and consequence viscosity increase. Furthermore, if the pipeline were not insulated, the heat generated by the transported fluid would melt the permafrost layer.
A common technique for insulating pipelines is to apply rigid polyurethane foam to the exterior of steel pipe sections before they are delivered to the field for installation. Typically, such pipe sections are fabricated in lengths of twenty or forty feet with about nine inches of bare pipe exposed at each end to permit the welding of adjoining ends without melting any preapplied polyurethane foam adjacent the ends. This means that after installation, a short length of the pipeline, say about eighteen inches, spanning the weldment joining the pipe sections remains uninsulated.
In ordinary climates, the uninsulated portion of the pipeline left after installation would be insulated by pouring polyurethane foam into a mold surrounding the uninsulated portion or by spraying such foam onto that portion. These application methods require, however, ambient temperatures of +40.degree. F. or above and such temperatures exist in many of the cold regions in question only for about one month each year. Further, these application methods may not be used during conditions of high humidity. At the present time, therefore, the adjoining ends of an entire length of pipeline may remain uninsulated for an extended period before conditions permit the foam application techniques just discussed. There exists, therefore, a need for some means of applying insulation to the uninsulated joints of a preinsulated pipeline immediately after the pipeline is installed and tested, regardless of ambient temperature or humidity.